1. Field of the Invention
The present invention relates to a steam turbine power plant.
2. Description of the Related Art
It is being demanded that a starting time of a steam turbine power-generating plant be further reduced for suppressed instability of the electric power in a grid-connected power system by connecting renewable energy, represented by wind power generation or solar power generation, to the power system. When the steam turbine is started up, however, steam abruptly increases in both temperature and flow rate. A consequential sudden increase in a surface temperature of the turbine rotor relative to an internal temperature thereof augments a radial temperature gradient and thus increases a thermal stress. An excessive thermal stress could shorten a life of the turbine rotor. In addition, if the change in the temperature of the steam is significant, differential thermal expansion due to a difference in heat capacity occurs between the turbine rotor and casing of the turbine. If the differential thermal expansion increases, this could lead to contact between the rotating turbine rotor and the stationary casing, and hence to damage to both thereof. When the steam turbine is started, therefore, there is a need to control the thermal stress of the turbine rotor and the differential thermal expansion thereof with respect to that of the casing so as to fall within a range of respective limit values.
In a known technique allowing for the above, before a steam turbine is started, the thermal stresses and differential thermal expansion that are estimated to occur during a definite period of time ahead from current time of day are calculated by prediction and then the start of the turbine is controlled so that the predictively calculated thermal stresses and differential thermal expansion fall within a range of respective limit values (refer to JP-2009-281248-A, shown as Patent Document 1 below).